This invention is a self-actuated, automatic device, especially a valve for control of fluid flow for application within a radiation field in a nuclear reactor.
Some applications exist in which it would be of benefit if a specific future operation of a valve could be planned in advance and designed as an inherent characteristic of the valve. The following is illustrative.
Fuel assemblies in nuclear reactors generally have nuclear and thermodynamic properties which change over the course of exposure to neutrons in the reactor. The content of fissile uranium 235 decreases in a fuel assembly during exposure to a neutron flux while the plutonium 239 content of a blanket assembly may increase. In the case of a fuel assembly, it may be desired to gradually decrease coolant flow through the assembly to match a gradual decrease in the assembly fission rate. In the case of the blanket assembly, it may be desired to gradually increase coolant flow through the blanket assembly to match a gradual increase in fission reactions.
Coolant flow through an individual fuel or blanket assembly can be controlled by inlet or outlet valves (or variable-size orifices) attached to the individual assemblies in the reactor. A problem lies in access to the vlave in the nuclear reactor. Fuel and blanket assemblies in a reactor are numerous such that any system for control of many valves from outside of the reactor would be extremely complex. Several schemes have been attempted to provide assemblies with variable-size orifices, but as yet no economically viable or practical system for true variability in orifice size has been discovered.
Consequently, it is desired to provide an automatic, self-actuated valve, which is of particular use as an orificing valve for use with nuclear fuel and blanket assemblies.